Glitch Stalls Juno Engine Burn at Jupiter

NASA's Juno spacecraft will remain in its looping, 53-day orbit around Jupiter until at least Dec. 11 after a possible problem was discovered with the spacecraft's main rocket motor.

Flight controllers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., had planned for Juno to perform a braking maneuver on Wednesday so that it could put itself into a 14-day orbit around the largest planet in the solar system.

But during a routine check of the spacecraft late last week, engineers discovered that two helium valves, which are part of the system to pressurize Juno's fuel, were not working as planned.

"The valves should have opened in a few seconds, but it took several minutes," project manager Rick Nybakken said in a statement. "We need to better understand this issue before moving forward with a burn of the main engine."

Ideally, the maneuver to adjust Juno's orbit takes place when the spacecraft is closest to Jupiter and the next time that happens will be on Dec. 11.

Scientists are compensating for the change of plans by turning on all of Juno's science instruments during its close approach to Jupiter on Wednesday, the day the orbit adjustment burn was scheduled to occur.

"The orbital period does not affect the quality of the science that takes place during one of Juno's close flybys of Jupiter. The mission is very flexible that way," lead scientist Scott Bolton, with the Southwest Research Institute in San Antonio, said in the statement.

Juno arrived at Jupiter on July 4 for a 20-month study to more about how and where Jupiter formed.